Cellular reception in or on moving vehicles such as cars, buses, trams, train and ships is often poor because the vehicles are moving through areas which are served by different transmission installations and because the vehicles are predominantly metallic structures which act as Faraday cages and therefore further attenuate cellular signals.
Moving vessels at sea encounter weak reception of mobile communication signals because, in addition to the above, base station antennas are primarily planned, positioned and installed on land in order to serve mainland hotspots. The sea routes along which vessels travel are not usually located in main radiation areas of base station antennas and are generally a long distance away from cellular towers, resulting in significant pathloss.
In order to address weak or poor reception, cellular repeater systems are often used. A cellular repeater (also known as cell phone signal booster or amplifier), is a system used for boosting the cell phone reception in confined or remote areas such as buildings, tunnels, ships and the like. Cellular repeater systems generally comprise three main functional units: a donor external antenna, a signal bi-directional amplifier, and an internal rebroadcast antenna or distributed antenna system.
Due to the translational movement of a vessel along a sea route, the cellular tower providing the best signal for use by the vessel will change; indeed, the direction from which the best serving donor signal is received may be at any azimuth direction—i.e. anywhere 360° around the vessel's horizon. Omnidirectional antennas radiate power uniformly in all directions in one plane, and are therefore selected for in-ship cellular repeater applications. However, omnidirectional donor antennas have extremely low gain (usually 0 dBi compared to the significantly higher gain offered by a typical directional antenna) as a result of the received power based on very low radio link budget between the donor cellular tower and the cellular repeater system (the radio link budget accounts for all of the gains and losses between the transmitter and the receiver). This affects the effectiveness and efficiency of such cellular repeater systems.
It is an aim of the present invention to mitigate at least some of the above mentioned drawbacks of the prior art.